Audio problem: When Kate is behind the bar, and the Gremlins are drinking beer and smoking, Kate says "Just don't bite me." Her mouth doesn't move at all when this is heard. (01:11:00)
Audio problem: When Billy is playing on the keyboard with Gizmo, the second key we see him hit should have been a higher tone, not lower, as it's toward the right end of the keyboard.
Answer: The original film was released before the PG-13 rating existed (it was one of the films responsible for its creation). Producers decided to remove some of the language and violence for the DVD release to avoid complaints about the PG rating.